This invention relates to a system for minimizing carbon dioxide emissions from a stationary source, and specifically for minimizing carbon dioxide emissions emanating from burning fossil fuels or extracting natural gas.
There is currently a great interest in reducing emissions of carbon dioxide (CO2) gases into the atmosphere. The amount of CO2 gas emitted into the air is cited as a factor contributing to global warming. CO2 gas is emitted whenever fossil fuels are burned, such as in automobile engines and coal burning furnaces used by power plants for the generation of power. Reductions in the amount of CO2 gases emitted by such processes is of increased importance and is a point of specific emphasis for government regulatory agencies. This is especially so for power plants burning large volumes of fossil fuels, emitting large quantities of CO2 into the atmosphere.
Currently systems for controlling and eliminating the CO2 from a breathable air supply are utilized in submarines, space vehicles and space suits. These systems utilize a CO2 sorbent bed composed of a plurality of amine sorbent beads disposed within a container. A stream of air containing CO2 is flowed through the container and the amine sorbent beads. The CO2 contacting the amine sorbent beads reacts therewith to become trapped within the container. The remainder of the breathable air recirculates into the controlled environment. Once the container has become saturated with CO2 such that further absorption of CO2 is inefficient, the breathable air stream is switched to a second container. The saturated container is then exposed to heat or reduced pressure to evolve or release the trapped CO2 for disposal or use in other systems. Such systems have proven effective and efficient for controlling CO2 content within enclosed environments, however this technology has not been applied to environments such as those encountered in the operation of a power plant or the extraction of natural gas.
It is therefore desirable to employ technology associated with controlling CO2 in enclosed environments to control exhaust emissions associated with burning of fossil fuels and extraction of natural gas.
A disclosed embodiment of this invention is a system and method for controlling carbon dioxide (CO2) emissions emanating from a gas source using sorbent beds containing a regenerable sorbent.
The system controls CO2 emissions formed from the burning of coal or natural gas by absorbing CO2 from a gas stream. The system is installed such that exhaust gases are communicated through a CO2 sorbent bed before being released into the atmosphere. The CO2 sorbent bed traps CO2 contained within the exhaust gas such that the now CO2 minimized gas is finally exhausted to the atmosphere. Another embodiment of this invention is installed to control CO2 content within natural gas extracted from a well. The gas extracted from the natural gas well is routed through the CO2 sorbent beds of this invention to control the amount of CO2 contained within the final product.
The system includes at least two sorbent beds with one operably associated with the exhaust gas stream. The particular sorbent bed communicates with the exhaust gas stream by way of an inlet conduit and inlet valve. The inlet valve directs the exhaust gas stream through the sorbent bed such that CO2 is absorbed and trapped. The outlet valves direct gas out of the sorbent bed. While one sorbent bed absorbs CO2, another sorbent bed is being regenerated to release trapped CO2 into a storage container for disposal or use in other processes.
Applying heat above a predetermined temperature to release trapped CO2 regenerates the sorbent bed. A vacuum source is in operable communication with the regenerating CO2 sorbent bed to draw the released CO2 out of the sorbent bed. Alternatively, a steam source is introduced through a steam inlet valve to heat the sorbent bed and release CO2. Steam heats the sorbent bed above the predetermined temperature to cause the release of CO2 from the sorbent bed and concurrently drive the CO2 out through the outlet valve.
A controller governs actuation of the heat source and of the vacuum source. The controller is also in communication with the inlet valve and the outlet valve to switch which sorbent bed, the gas stream flows. The controller alternates flow of the gas stream between the sorbent beds, such that one of the sorbent beds is always regenerating, while another sorbent bed is in communication with the gas stream.
A cooler is in operable communication with the sorbent bed that is currently in communication with the gas stream to regulate temperatures within the sorbent bed. Absorption of CO2 generates a great deal of heat, and the sorbent bed works most efficiently at cooler temperatures. The cooler is actuated in response to signals from the controller to maintain a desired optimal temperature for the sorbent bed.
The sorbent beds include a regenerable CO2 sorbent. Regenerable CO2 sorbents are capable of repeatedly trapping and releasing CO2 for many cycles and are therefore desirable for CO2 removal applications including exhaust gases exhausted from a smoke stack. Preferably, the sorbent is an amine sorbent applied to a support structure to form a plurality of amine sorbent beads. The amine sorbent beads are packed into each sorbent bed to contact the gas steam.
In operation, the controller of the system actuates the inlet and outlet valves to direct the gas stream through at least one of the sorbent beds. The sorbent disposed within the sorbent bed forms a loose molecular bond with the CO2 to trap the CO2 within the sorbent bed. The remaining gas is directed out of the sorbent bed either to a storage tank or through a smokestack. The controller actuates the cooler to govern the temperature of the sorbent bed in contact with the gas stream to maintain an optimal temperature.
The CO2 sorbent bed is placed within the gas stream, for a predetermined duration calculated to optimize CO2 absorption. The controller will then actuate the inlet and outlet valves to divert the gas steam to another sorbent bed. The CO2 saturated sorbent bed is then regenerated in preparation for another absorption cycle.
The system and method of this invention employs technology for controlling CO2 in enclosed environments to control exhaust emissions associated with burning of fossil fuels and with natural gas production.